Sigma 30mm f/2.8 on the NEX-7.

The Sony NEX platform is still relatively new on the market and the lens range is still relatively modest, so I was quite excited to hear that Sigma announced two new primes for the NEX mount, a 19mm and 30mm f/2.8. This is a review of the 30mm, which gives the same angle of view as a 45mm on a full frame 35mm camera. Sigma is at present the only third party lens manufacturer producing primes for the NEX mount.

The lens comes in a dark gray finish (a tap lighter than the NEX-7 black and less shiny). It is delivered with lens caps and a lens case but no shade. Sigma argues that their new coatings prevents flare without the need for a shade. The shade from the Sony kit zoom does not fit. Filter mount diameter is 46mm. Diphragm is 7 blades, but I have not tested the bokeh. Minimum focus distance is 0.3m (0.98ft) and, unfortunately for the video inclined, focus is quite loud with a distinct click when focus is attained.

One may wonder what is the use for a 30mm prime lens when NEX cameras come with a 18-55mm standard zoom. The advantages are as follows:

  • some photographer prefer prime lenses (I do)
  • prime lenses are usually faster, this lens is a stop faster than the standard zoom at 30mm (which, frankly is not that much)
  • prime lenses can be smaller, so called "pancake lenses" are of great interest for a system selling itself on size
  • prime lenses are easier to correct than zooms and can therefore be sharper.

So is the Sigma 30mm f/2.8 that small? Here are some comparison views between the Sony 16mm f/2.8 pancake, the Standard NEX 18-55 zoom and the Sigma 30mm f/2.8. As you can see, it is more compact than the zoom but not as small as the pancake. The gain over the zoom is real, though.

The standard zoom, pancake and Sigma 30mm on the NEX-7 The standard zoom, pancake and Sigma 30mm size comparison

What about optical quality, then? After all, the NEX platform already has the Sony / Carl Zeiss 24mm f/1.8, which is as big as the standard zoom and principally sells itself on aperture and quality. The Sigma is a fifth of the price, it does not have the f/1.8 aperture, but does it have the quality? Considering that the NEX-7 puts quite a strain on lenses with its 24 mpix resolution, what can we expect from a 200€ lens?

Designing compact lenses for the NEX platform is not easy, because of the small registration distance. The Sony Pancake, in particular, is known to have its share of problems when combined with the NEX-7. People using lenses designed for rangefinder have also noted that some of them give poor results, exhibiting extreme corner darkening or color shift across the frame. My understanding is that the sensor response is poor when light rays hit it at a steep angle, as is the case for rangefinder lenses. Sigma said that they have addressed this issue by designing the lens as telecentric and indeed the rear lens is surprisingly large compared to the front one:

 Sigma 30mm rear lens Pancake, Sigma 30mm and 18-55 zoom front views.

But is the lens sharp?

Testing sharpness for an amateur is not very easy, because the common methods like photographing a newspaper hung on a wall are fraught with potential errors. The method is used is different: is take a picture of a subject far away. Everything is at the same distance, since everything is far away. There are no consideration of the target needing to be perpendicular to the lens axis or flat. There is little risk or errors. As a bonus, lenses are tested at distance more akin to the distance they are used in practice: some optics give poor results at the typical distance used for a test target, but are good when the subject is further away or vice-versa. To insure that there is a target from the center of the lens till the corners of the frame, I took a picture of the city skyline and oriented it corner to corner, like this:

 Horizon skyline as diagonal, corner to corner target (taken with the Sigma 30mm at f/2.8)

By examining the difference between the corners and the center, or the difference between the results at different apertures, or the difference between different lenses, we can see which lens is sharp and which lens is… less sharp. It is a very simple procedure, but quite informative for the photographer. For example, here are the results for the 16mm pancake at f/2.8:

Pancake center crop Pancake lower corner crop

While the pancake has good center sharpness it exhibits very poor corners wide open. The difference is obvious.

And the Sigma?

This is the good surprise: at f/2.8 already, it is sharp corner to corner. It vignettes a little bit wide open (disappears when stopping down) and has a little bit of lateral chromatic aberration (which does not disappear when stopped down but is easy to correct), but apart from that it is close to be a perfect lens. Recommended.

Sigma 30mm f/2.8 center crop Sigma 30mm f/2.8 lower corner crop

You may download the full resolution pictures at f/2.8, f/4, f/5.6, f/8 and f/11 from my flickr account: http://www.flickr.com/photos/jerome_munich/sets/72157629651034759/detail/

The views and opinions expressed in this article are those of the author and do not necessarily reflect the views and opinions held by dpreview.com or any affiliated companies.

Comments

Total comments: 19
David Smith - Photographer
By David Smith - Photographer (4 months ago)

I think that even today this cheap little Sigma most certainly is one of the most exciting lenses ever made for the NEX system. There is some CA and vignetting, but apart from that, this lens delivers sharp and contrasty results that rival those from expensive lenses like the Zeiss 24mm f/1.8. In Europe you can pick up the first version of the Sigma brand new for as little as 129 euros (secondhand for about 75 euros). That's a super bargain if you ask me. The Sigma 19mm f/2.8 failed to impress me.

0 upvotes
Hubertus Bigend
By Hubertus Bigend (Mar 26, 2012)

I think the crops are not really sharp – my guess is that the air was not calm enough to get proper long-distance sharpness (possibly would have made supertele shooting quite impossible that day). I think the originals on your Flickr page show closer buildings which correspond better to your praise of the lens, though!

Anyway, thanks for showing us. Although it remains one of the least exciting lenses of late, it actually might make sense as a cheap but good standard prime for both NEX and Micro-FT, after all. Of course it would've been nicer if it was f/2.4 or f/2, or if it had at least some macro capabilities...

2 upvotes
jerome_munich
By jerome_munich (Mar 31, 2012)

Something went wrong with the crops, when you click on them they are enlarged 2 times. This is why they do not appear perfectly sharp. On my flick account you have the native resolution.

0 upvotes
madmaxmedia
By madmaxmedia (Mar 25, 2012)

The short registration distance doesn't make it hard to design lenses, any more than a longer registration distance. The lens elements can be as far away from the sensor as the designer wants, the registration distance only governs the distance of the mount from the sensor, correct?

1 upvote
jerome_munich
By jerome_munich (Mar 26, 2012)

You are correct, yes.

1 upvote
davidstock
By davidstock (Mar 25, 2012)

i've been experimenting with downloaded files from this lens to see what i can do to correct the CA and recover any lost detail. in the end, i got much better results than i had feared.

it's all about moderate use of the red/cyan slider and careful sharpening technique.

so i'm gonna give this lens a chance. for $200, it seems like a good deal. not sure i'll prefer it to the manual focus lenses i use now, but it's nice to have autofocus sometimes.

thanks for sharing your tests, Jerome. they are simple, well done, and useful. looking forward to your tests of the 19mm.

2 upvotes
eths
By eths (Mar 24, 2012)

Greetings to Munich from Munich... Thank you very much for doing this.

The initial impression seems promising, especially for the price.

0 upvotes
AdamT
By AdamT (Mar 24, 2012)

my 16mm Pancake is incomparibly better than the DUD sample above - Sony really need to get sample consistency with their Kit lenses, I had a Dud 18-55 like that . I`ve got good samples of both now

0 upvotes
jerome_munich
By jerome_munich (Mar 24, 2012)

I don't think that my copy is bad, at least it appears to be correctly centered. I have another copy which is worse.
Keep in mind that this is f/2.8 and the extreme corner. It also seems that dpreview enlarges the image by a factor of 2.

There are full size downloads of horizon pictures taken with the 16mm (and the kit zoom, and many A-mount lenses) on my flickr account.

0 upvotes
futile32
By futile32 (Mar 24, 2012)

Thanks, had mine pre-ordered for a while, but have been eager to see a review on it. Looks like its a good investment for the price.

Would have liked to hear some feedback on the Sigma AF compared to Sony, and how it functions with MF.

0 upvotes
jerome_munich
By jerome_munich (Mar 24, 2012)

The AF works just like on a Sony lens, but it is noticeably noisier and a bit slower. The camera needs to focus back and forth to detect the focus point (that is how it works with all lenses), on the Sigma you perceive the process better than on the kit zoom, meaning it is a bit slower.

Manual focus works just fine, the feeling is similar to a manual focus lens. I can't hear any noise when manual focussing.

0 upvotes
futile32
By futile32 (Mar 25, 2012)

thanks good to know

0 upvotes
jerome_munich
By jerome_munich (Mar 24, 2012)

Has a fast standard prime being announced beyond the CZ 24mm? I thought it was a fast standard zoom?

Comment edited 2 minutes after posting
0 upvotes
straylightrun
By straylightrun (Mar 24, 2012)

E-mount version of the 30/2.8 is now in stock at BHphotovideo. Tempting, but I think I'll wait for the specs of the Sony "fast standard prime".

0 upvotes
cptrios
By cptrios (Mar 24, 2012)

Thanks! I've been waiting for this for ages now, and these results have me excited. Any idea when the 19mm might pop up?

1 upvote
jerome_munich
By jerome_munich (Mar 24, 2012)

I should get a 19mm on monday.

1 upvote
cxsparc
By cxsparc (Mar 24, 2012)

Thanks for your efforts!
Could you possibly also make a comparison shot of the kit corner to corner? That would be great, since the kit is supposed to be quite good at that focal length.
Br,
Christian

0 upvotes
jerome_munich
By jerome_munich (Mar 24, 2012)

If you had looked at my flickr account you would have found the same kind of pictures taken with the kit zoom... ;)

0 upvotes
sean lancaster
By sean lancaster (Mar 24, 2012)

The kit wide open corners doesn't look very good to me. Thanks for sharing these.

0 upvotes
Total comments: 19